1. Field of the Invention
The present invention generally relates to an antenna device, and particularly relates to an antenna device including a ground section and an element section.
2. Description of the Related Art
Recently, with the development of computers and peripheral devices, it has been desired to connect computers to peripheral devices without using cables.
As a technology for performing wireless communications between computers and peripheral devices, an Ultra-Wide Band (UWB) technology is drawing attention in that UWB enables communications with high transmission capacity. The use of the UWB in a frequency band of 3.1-10.6 GHz was approved by the U.S. Federal Communication Commission (FCC) in 2002.
The UWB system is a communication system for transmitting pulse signals in an ultra wide band. Therefore, antennas for UWB communications need to have a structure that allows transmission/reception of the pulse signals in the ultra wide band.
As an antenna to be used at least in the frequency band of 3.1-10.6 GHz approved by the FCC, Non-patent Document 1 discloses an antenna in which a conical or teardrop-shaped power feeder is disposed on a flat base plate.
The antenna of Non-Patent Document 1 is, however, large because the conical or teardrop-shaped power feeder is disposed on the flat base plate. It is therefore desired to reduce the size and thickness of the antenna.
Meanwhile, as a loop antenna for communications in a low frequency band, Patent Document 1 discloses an antenna device in which an element section is a conductive pattern formed on a flexible substrate.
Patent Document 1: Japanese Patent Laid-Open Publication No. 2000-196327
Non-Patent Document 1: Takuya Taniguchi and Takehiko Kobayashi (Tokyo Denki University) “An omnidirectional and low-VSWR antenna for the FCC-approved UWB frequency band” proceedings of the IEICE (Institute of Electronics, Information and Communication Engineers) General Conference in 2003 (presented at room 201 on March 22)